Asphalt Pavement Materials Research Articles

923 PERFORMANCE CHARACTERISTICS OF THERMOSETTING POLYURETHANE MODIFIED ASPHALT BINDER AND ITS MIXTURES

A new thermosetting polyurethane modified asphalt (TPUA) pavement material was developed to solve the unbalanced performance of traditional bridge deck pavement materials. Compared with the conventional bridge deck pavement materials, this work comprehensively evaluates the pavement performance of the TPUA binder and its mixture. The results indicate that the TPUA binder gradually shows elastic material properties at high temperatures and has excellent deformation resistance. The low-temperature flexibility of the TPUA binder is much better than that of SBS asphalt and epoxy asphalt (EA) binders. The TPUA binder is a viscoelastic material at low temperatures, and its creep meets the Burgers constitutive model. Moreover, the TPUA binder also has excellent mechanical properties and flexibility. In addition, the TPUA mixture has excellent mechanical properties, high-temperature deformation resistance and moisture stability. Its crack resistance at room temperature and low temperature is much better than those of SBS asphalt and EA mixture. This work will help us continue the development and performance research of TPUA pavement materials.

Modifying Effect and Mechanism of Polymer Powder on the Properties of Asphalt Binder for Engineering Application.

For achieving the better modifying effect of polyurethane on asphalt pavement materials, the PUA powder modifier was prepared with fine grinding at the glass transition temperature, and polyurethane-modified asphalt (PUA-MA) with different dosages of modifier was prepared. The impact of the PUA on the physical properties of asphalt binder was studied. The modifying mechanism of PUA on asphalt was explored by investigating the thermal performance and chemical composition of asphalt (thermogravimetric analysis, differential scanning calorimetry test, and Fourier transform infrared spectroscopy). The micrograph of the interactive interface was characterized by scanning an electron microscope. Furthermore, the rheological properties of PUA-MA were also investigated and analyzed. The results indicated that the PUA had a dense structure with few pores on the surface. After mixing with asphalt, it altered the asphalt's internal structure via physical fusion and chemical reaction (carbamate formation). PUA improved the thermal stability of asphalt, enhanced the asphalt's thermal decomposition temperature, and further reduced the thermal mass loss while decreasing the glass transition temperature. The addition and dosage increase in the PUA modifier significantly improved the softening point, viscosity, complex shear modulus, and rutting factor of asphalt. Also, the PUA could improve the elastic recovery ability of asphalt and enhance the rutting resistance of asphalt at high temperatures. However, the crack resistance at low temperatures was not effectively improved (ductility and penetration decreased). When the dosage was 6-9%, PUA-MA had the best high-temperature performance, but asphalt showed poor low-temperature performance at this dosage. This study provides a theoretical reference for popularizing and applying polyurethane as an asphalt modifier in road engineering.

A literature review: asphalt pavement repair technologies and materials

Asphalt pavement is the most widely used type of pavement in the world and is mainly utilised in the construction of infrastructures such as highways, urban roads, parking lots and airstrips. Pavement maintenance technology and materials are gradually developing towards systematisation and diversification with the extensive use of asphalt pavement. Choosing more economical technologies and fast and sustainable materials is the future of asphalt pavement maintenance work. This paper provides an overview of asphalt pavement repair technology and asphalt pavement repair materials. It categorises and summarises pavement repair technologies, which include cost-effective technologies such as crack sealing, overlay, seal coats and hot in-place recycling. Further, it summarises the repair materials applied in repair technologies and compares the performance, cost-effectiveness and sustainability of these materials. The study shows that asphalt and cement are the most commonly used repair materials. The higher-potential, more economical and more sustainable materials for asphalt pavement repair include epoxy resin, polyurethane and hydrogel. The future of asphalt pavement repair requires advancing towards rapid, sustainable, environmentally friendly and economical repairs. A survey indicates that in addition to improving the performance of existing repair materials (e.g. modified asphalt, binder processes, material composition or ratios), attention can be given to new materials such as polyurethanes and hydrogels that have the potential for rapid repair and are low cost. More research can be done to perfect the application of new materials in road engineering.

Assessment of microplastics production from waste plastics-modified asphalt pavement

Post-consumer recycled plastics (PCRP) have been increasingly utilized in asphalt pavement applications as the world moves towards a circular economy. However, it is unknown whether microplastics (MPs) could be generated in significant amounts during the subsequent pavement life cycle. This study developed methods to detect and quantify the potential microplastic generation from asphalt pavement materials containing PCRP (specifically, linear low-density polyethylene) using the Hamburg wheel-tracking test and a water permeability test. MPs were quantified by Nile Red staining followed by fluorescence microscope imaging. Environmental scanning electron microscopy (ESEM) and energy dispersive spectroscopy (EDS) were further conducted to characterize the nanoscale morphology of the embedded PCRP. The results showed that the generated MPs could reside at water/air interface, in bulk water, or with asphalt binder and aggregates in the sediment; and their amounts varied depending on the polyethylene dosage and type. The potential environmental impact of MP production from PCRP-modified asphalt pavement needs to be examined under the context of MP particle releases from other emission sources, notably, the tire wear particle generation when rubber tires meet the road. Our assessment indicated that while there was a potential of MPs release from the PCRP-modified asphalt, the up-scaled level of their release from a pavement was estimated to be about three orders of magnitude less than the tire wear rubber particles.

Plastic Waste Sheets Effects on Reclaimed Asphalt Pavement Performances

Abstract This paper aims to examine physical and mechanical performances of a Reclaimed asphalt pavement (RAP) material reinforced with 5 to 15 mm size sheets of plastic waste. The three types of plastic used in the study are: low density polyethylene (LDPE), high density polyethylene (HDPE) and polyethylene terephthalate (PET) with 1%, 1.5%, and 2% dosage by weight of aggregates. Obtained Duriez test results testify to a 9% to 30% improvement in moisture resistance for all types of plastic compared to virgin mixture while for LDPE waste plastic type workability test attests an acceptable compaction condition for RAP material with less than 1.5% of waste plastic. Nevertheless, it has been noticed an increase in void index and compaction difficulties starting from 1.5% dosage, resistance to rutting has also improved with the addition of waste plastic, an improvement in fatigue strength was also observed particularly at 2% dosage.

Life Cycle Carbon Emissions and an Uncertainty Analysis of Recycled Asphalt Mixtures

The efficient recycling of road materials is an effective way to reduce carbon emissions. Approximately 400 million tons of waste asphalt pavement materials is generated annually in China, but the utilization rate is less than 50%. In this paper, a whole life cycle CO2 emission calculation model for recycled asphalt mixtures is established, and an uncertainty analysis is carried out on the basis of this model. The steps in the recycled asphalt mixture stage with the greatest impact on emissions are identified. The life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction phases based on the carbon emission trends in the four phases. First, recycled asphalt mixtures are considered, and the carbon emissions along a two-way four-lane highway are analyzed based on the relevant carbon emission factor and other known data. The carbon dioxide emissions of each stage are also compared to identify the key links among stages. Then, the carbon emissions of hot-recycled asphalt mixtures are compared with those of ordinary asphalt mixtures and cold-recycled asphalt mixtures in each stage. Finally, an analytical uncertainty study of recycled asphalt mixtures is conducted using uncertainty modeling in different scenarios. Based on the quantitative results of the carbon emission calculations through life cycle assessment (LCA), future measures for reducing carbon emissions from recycled asphalt mixtures are proposed.

A novel method for enhancing coating performance of emulsified asphalt mortar to RAP in cold recycled mixture

Emulsified asphalt mortar (EAM) is prone to agglomeration and has poor adhesion to reclaimed asphalt pavement material (RAP) with residual-aged asphalt, which can deteriorate the durability of emulsified asphalt cold recycled mixture (EA-CRM). In this work, silane coupling agent (SCA, 3.75 wt% and 6.25 wt% by weight of emulsified asphalt) and polycarboxylate superplasticizer (PCS, 3.75 wt%, 7.5 wt%, and 11.25 wt%) were used to modify the EAM in order to improve the coating performance of EAM on RAP. Seven kinds of samples with different modifier dosages were prepared. Modification mechanism, micro-morphological changes, workability, rheological property, and coating degree of EAM on RAP were investigated. Furthermore, action mechanism of the SCA/PCS composite modifier (SPCM) in EAM/RAP and the cost-benefit were analyzed. Results show that EAM is physically modified by SPCM. Carboxylic group and polyethylene glycol side chain in PCS possess excellent improvement on the workability of EAM, while silanol group generated by hydrolysis of SCA plays a major role in improving coating performance. An appropriate dosage of SPCM can improve the workability of EAM, and enhance its shear deformation resistance and elastic properties. Meanwhile, SPCM can improve the coating degree of EAM on RAP, but SPCM with a PCS dosage exceeding 7.50 wt% can cause EAM to slightly detach from RAP surface. Therefore, 6.25 wt% of SCA and 7.50 wt% of PCS were proposed to modify EAM to obtain the best overall performance. The application of SPCM had a good cost performance and additional environmental benefits based on the optimal dosage. This work provides a novel method to enhance the coating performance of EA-CRM while facilitating the expansion of RAP applications.

The Significance of the Factors Increasing the Asphalt Pavement Recycling Rate in the Country, Determined Using Multiple-Criteria Decision-Making Methods

Asphalt pavement, a component of transport infrastructure, deteriorates under the influence of destructive factors. The damages which have occurred during its period of use are repaired and the asphalt pavement is recycled when its further rehabilitation is economically and technically irrational. The material from the asphalt pavement layer that has reached its limit state is milled out or broken and crushed and then is repeatedly used in the production of hot-mix asphalt (HMA) or warm-mix asphalt (WMA) mixtures. In this paper, the dynamics of the percentage recycling ratio (RR) of old asphalt pavement material was investigated. RR represents the quantity of reclaimed asphalt pavement (RAP) used in the production of HMA and WMA mixtures in Europe and the USA, divided by the total amount of RAP prepared in the country. Factors and goals affecting it are analyzed. An original system of 10 criteria that increase the RR country has been created. Decision makers do not know which factors have the maximum influence in increasing the use of RAP and this should go in connection with environmental pollution reduction and achieving economic utility. By applying different multiple-criteria decision-making (MCDM) methods and using the importance given to these criteria by 14 experts, the normalized subjective weights of the criteria were determined. Analytic hierarchy process (AHP), rank correlation, average rank transformation into weight—linear (ARTIW-L) and non-linear (ARTIW-N), and direct percentage weight (DPW) methods were used in the study. The results show that the RAP recycle rate is close to 100% in countries with a sustainable economic background. In the Baltic countries, it is mostly increased by the adequacy of regulatory documents, the strategy promoting asphalt recycling in the country, and the homogeneity and classifying of RAP. The number and capacity of RAP stocks, the number and productivity of asphalt milling equipment and the wear and tear of the asphalt pavement have the least influence on the increase in RR. The opinions of experts in assessing the significance of all criteria are consistent. The averages of the weights of criteria determined by four MCDM methods (AHP, ARTIW-L, ARTIW-N, DPW) made it possible to obtain more reliable results. These results can be used to make strategic decisions and to create a plan of practical actions to increase the RAP recycling rate in the developing countries.

The influence of recycled asphalt pavement materials on low and intermediate fracture behavior of asphalt concrete (AC) after exposing to different thawing and freezing periods

The effects of compaction process, mixture type and environmental conditions on mode I cracking resistance of asphalt concrete (AC) materials was investigated experimentally. To do that, a large number of edge notched disc bend specimens containing 0, 25 and 50% recycled asphalt mixture (RAP) material and exposed to different numbers of thawing and freezing cycles (0 to 10 cycles) were fractured. The critical values of stress intensity factor and fracture energy indexes were obtained for the AC mixtures at three test temperatures of −25, 0 and + 25 °C. Based on the results, the fracture resistance capacity of the AC mixture was decreased by increasing the RAP content, number of thawing/freezing cycles and decreasing the test temperature. The effect of thawing/freezing cycles on decreasing the cracking resistance was more pronounced for the first cycles and the variations of fracture toughness and fracture energy values with the numbers of thawing/freezing cycles showed a plateau form for higher numbers of cycles. The fracture curves of the tested samples manufactured using the Gyratory compaction method was upper than the related curves of samples made by Marshall compaction method. The sensitivity of fracture results (i.e., gradient of reduction in the fracture resistance versus freeze/thaw cycles) became low by increasing the test temperature.

Effect of re-aging on chemical and rheological properties of waste engine oil rejuvenated asphalt binder

The use of rejuvenator can potentially restore original properties of reclaimed asphalt pavement (RAP) materials to achieve the purpose of reuse, but less attention has been paid to the aging properties of rejuvenated asphalt binders. In this study, original asphalt binder, aged binder and the rejuvenated binders with 3 %, 6 %, and 9 % of rejuvenator by total weight of binder were prepared first. Then the five rejuvenated binders were subjected to the oven aging. Based on the results from Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheometer, the chemical and rheological properties of the five binders were investigated due to re-aging. It is showed that the of carbonyl index of the rejuvenated binders and original binder increase rapidly during the fast-aging state and then slowly during the constant-aging state, while aged binder increases approximately linearly. The rheological properties indexes such as complex shear modulus, phase angle δ, crossover frequency, crossover modulus, rheological index, G-R parameter and rutting factor of the five binders were determined, and the variation of these indexes are similar or opposite to carbonyl index during aging. Aging performances of the five binders were investigated using the oven aging indexes. It is showed the rejuvenated binders with more dosage of rejuvenator have faster aging rate and more obvious effects on the aging rheological behavior. The rheological properties of the aged binder are less affected by the re-aging. Among the rheological property indexes, the G-R-based oven aging index is most susceptible to the re-aging. There are some certain close relationships between the chemical property change and rheological property evolution during re-aging for the five binders, without considering the aging times and the dosage of rejuvenator.

Material and mix design aspects of hot recycled asphalt mixes: A review.

Sustainability in road construction can be achieved by integrating recycled materials in the production of new pavement. One such approach is using reclaimed asphalt pavement materials (RAPM) in hot mix asphalt (HMA). Successful implementation of RAPM in HMA can only be achieved by having good comprehension of the essential material characterisation and design process. The main objective of this review is to summarise the literature and provide a keen understanding of the characterisation of materials involved (RAPM and rejuvenators) and mix design, by giving due consideration to the interaction of virgin and recycled materials. Widely used techniques for extraction and recovery of reclaimed asphalt pavement (RAP) binder have been reviewed. The advantages and disadvantages of different characterisation techniques are identified. The effect of various factors on the volumetrics of the recycled mixes is presented. Insight in to the requirements of a rejuvenator by taking into account the changes in binder after ageing is provided. Aspects that need further exploration to normalise and increase the confidence of RAPM in HMA are also highlighted as the future recommendations.

Application of Modified Asphalt in Municipal Roads

The article expounds modified asphalt technology by introducing commonly used modifiers and fillers and analyzing the construction technology of modified asphalt. The use of modified asphalt in municipal roads provides new alternatives for asphalt pavement materials, but also solves the existing construction problems and reduces project costs. Therefore, the research and application of modified asphalt using new materials and new processes is a crucial aspect in road construction.

Characterization of Self-healing Properties of Asphalt Pavement Materials Containing Carbon Nanotubes: from the Binder and Mix Level based on Grey Relational Analysis

Asphalt pavement cracks not only reduce road life and affect traffic safety but also increase maintenance costs. These issues can be solved significantly if microwave heating (MH) technology is applied based on the self-healing mechanism. This work aims to adopt carbon nanotubes (CNTs) to modify asphalt binders to accelerate their self-healing properties. Thermal conductivity and diffusivity, high-temperature rheological characteristics, and fatigue resistance were conducted to investigate healing potential from binders level; semicircular bending (SCB) tests and MH test were used to assess the fracture and self-healing properties from mix level; Grey relational analysis (GRA) was employed to study the relevance of asphalt binder properties on the healing properties of mixes. Results indicated that CNTs could improve asphalt binders' thermal conductivity, thermal diffusivity, high-temperature deformation resistance, and anti-fatigue properties. However, the Jnr-diff results suggest that the content of CNTs needs to be controlled within 1.0%. From the mixtures perspective, samples with 1.0% content of CNTs can achieve the best fracture performance and healing efficiency with excellent heating uniformity and no overheating problems. Furthermore, thermal performance strongly correlates with mixtures' healing indexes. This research addresses the maintenance of asphalt pavement cracks, which is essential for long-life pavements and sustainable road development.

Advancements in Phase Change Materials in Asphalt Pavements for Mitigation of Urban Heat Island Effect: Bibliometric Analysis and Systematic Review.

This research presents a dual-pronged bibliometric and systematic review of the integration of phase change materials (PCM) in asphalt pavements to counteract the urban heat island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably, Chang'an University in China has emerged as a leading contributor. The systematic review addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM leakage prevention in asphalt, and effects on mechanical properties. The findings identify polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCM due to their wide phase-change temperature range and significant enthalpy during phase transitions. While including PCM can modify asphalt's mechanical attributes, such mixtures typically stay within performance norms. This review emphasises the potential of PCM in urban heat management and the need for further research to achieve optimal thermal and mechanical balance.

Study on the Adhesion Characteristics of Asphalt-Aggregate Interface in Cold Recycled Asphalt Mixtures

The reclaimed asphalt pavement materials have been used for sustainable cold-recycling, significantly benefiting air quality and resource conservation, while its microscale interface properties greatly affected road performance during the cold-recycling processes. In this investigation, the cold recycled asphalt mixtures were prepared with different mixing proportions, considering the effects of cement content and mixing water amount. The adhesion characteristics of the asphalt-aggregate interface in different cold recycled asphalt mixtures have been comprehensively investigated based on the atomic force microscopic (AFM). The microscale morphology and the adhesion properties, including roughness, inclination angle, adhesion force, Derjaguin–Muller–Toporov (DMT) modulus, and dissipated energy were evaluated at the interface and noninterface regions. The micromorphology results showed that the addition of cement could enhance the roughness and inclination in interface regions. In addition, the content of mixed water showed the most significant effect when the water amount was 80%. The results showed that the adhesion force, DMT modulus, and dissipated energy increased with the addition of cement, indicating that the cement could improve the microscale mechanical properties of cold recycled asphalt mixtures. With the increase of mixing water content, the adhesion characteristics showed varied results, and the optimum water content of 80% contributed to the adhesive properties. In addition, the adhesion force, DMT modulus, and dissipated energy were all higher in the interface region by comparing with the noninterface region. The correlations between the macroscale splitting tensile strength and microscale adhesion characteristics of cold recycled asphalt mixtures were established.

Repurposing Waste Polyurethane into Cleaner Asphalt Pavement Materials: Laboratory Investigation

Repurposing Waste Polyurethane into Cleaner Asphalt Pavement Materials: Laboratory Investigation

Characterization of Recycled Asphalt Pavement Materials for Use in Hot-Mix Asphalt Mixes

Abstract The use of recycled asphalt pavements (RAPs) has been a common practice in recent times owing to the sustainability aspect as well as the cost savings. Characterization of RAP is a challenging task because of the high variability in RAP, which can be associated with several factors such as the source, milling method, and processing techniques. RAP material characterization requires a sophisticated material testing facility and is time-intensive. A round-robin test organized by the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM) Technical Committee 237-SIB has resulted in a new characterization protocol that is primarily intended for new construction, rehabilitation, and maintenance requirements of pavements utilizing RAP. The current study has adopted the RILEM recommendations to categorize RAP from various sources using basic tests: gradation and cohesion. RAPs obtained from seven sources, including artificially aged RAP, were investigated in the current study, and the tests were carried out on 100 % RAP. The allowable proportion of RAP that could be used for the hot-mix asphalt mix design was computed for all seven RAP sources using the blending charts. Furthermore, significant correlations were obtained between the allowable RAP content and the cohesion indices. The observations from this study suggest that basic tests, such as cohesion tests, can reduce the need for complicated test procedures to some extent and can be very advantageous for extensive field projects using RAP.

Feasibility of determining asphalt pavement condition from falling weight deflectometer test and finiteelement model updating.

Determination of pavement internal condition froma non-destructive field test is a persistent topic for its practical necessity and difficulty. It is essentially an inverse problem calibrating pavement material and structural properties from pavement responses. Considering the intrinsic complexity of asphalt pavement materials (e.g., time and temperature dependencies of asphalt mixture and stress dependency of unbound granular materials), this problem has become a typical high-dimensional optimization problem with a large and diverse set of calibrated parameters. This study investigated the feasibility of artificial intelligence-based finiteelement model updating in addressing this problem, and focused on theaccuracy as well as stability of the backcalculated results. For a comprehensive evaluation of this method, theeffects of its components such as the surrogate model representing the pavement system, theapplied pavement response, theoptimization algorithm and thebackcalculation scheme were characterized. Finally, we found thatthe sensitivity of applied pavement responses to thebackcalculated pavement condition, the number of applied pavement responses and the balance between the backcalculated pavement condition and theapplied test were of significant importance to achievingaccurate and stable backcalculation results. Corresponding modifications were recommended to be conducted in future research for improving the performance of the proposed backcalculation method. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'.

Shrinkage of Cold Recycled Cement-Treated Mixtures of Asphalt Pavement Materials

Abstract As with other chemically stabilized materials, cold recycled cement-treated mixtures inherently shrink. Shrinkage cracks might accelerate the rate of pavement deterioration. The research reported here aimed at studying variables that may affect the shrinkage of recycled mixtures. An experimental plan was set to evaluate the effects of cement and reclaimed asphalt pavement (RAP) contents and curing time on the shrinkage of such mixtures with different recycled base course materials (namely cement-treated base [CTB], soil-cement [SC], and lateritic soil [LS]). Previously studied recycled mixtures with graded crushed stone (GCS) base course material were also considered in the analysis. From test results and statistical analysis, it was concluded that the finer the recycled mixture (with SC and LS base course materials), the higher the shrinkage potential. Conversely, coarser mixtures (with CTB and GCS as base materials) tend to shrink less. Accordingly, increasing RAP contents might help to reduce the shrinkage of finer mixtures because of coarser RAP gradation. Shrinkage increases with time and shows higher increasing rates at the early stages. Statistics showed that a stronger curing time effect occurs by the third week, and because of that, it is important to avoid moisture loss at the early stages. For the levels considered (1–7 %), cement content did not greatly impact the shrinkage, although it was statistically significant in most cases. Statistical analysis confirmed this, contradicting the practice of often adopting low cement contents to reduce shrinkage hazards.

Laboratory Evaluation of Emulsion-Treated Base Layer Mixes Incorporating Reclaimed Asphalt Pavement Materials

Emulsion-Treated Base (ETB) is one of the most preferred base layer stabilization methods in which dense graded aggregates are treated with a slow setting bituminous emulsion. To reduce the cost of ETB and minimize the need for virgin aggregates, it is essential to evaluate the possibility of incorporating higher dosages of Reclaimed Asphalt Pavement material (RAP) in ETB. The present study evaluates the effect of RAP incorporation in ETB at dosages of 0%, 25%, 50%, 75%, and 100%. The effects of RAP incorporation were studied in terms of RAP mixing and RAP blending methods. RAP mixing is a process in which a definite proportion of RAP is added to virgin aggregates of a given gradation without a target gradation, while in RAP blending, virgin aggregates of required aggregate sizes are blended to RAP with the objective of achieving a targetted dense aggregate gradation. In this study, RAP was characterized using cohesion tests, fragmentation tests, and other physical properties recommended by the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM) Technical Committee. When 50% RAP was added to ETB using the RAP mixing method, the Maximum Dry Density (MDD) of the mix decreased by 4.4%, but in using RAP blending, the reduction in MDD was only 1.3%. ETB prepared with up to 75% RAP, 3% emulsion, and 1% cement, using the RAP blending method, was found to satisfy the minimum indirect tensile strength requirement of 225 kPa (specified by TG 2 2009 and IRC 37 2012), and exhibited appreciable rutting resistance and a tensile strength ratio of more than 0.7. This study identified that 50% RAP incorporation in ETB using blending gives the best performance in terms of cohesive and adhesive strength, moisture resistance, and resistance to permanent deformation.